It's been a rough summer for creosote bush gall-hunting locally - poor rainfall this summer meant no fresh leaves. I tried to find some for the September gall week project but they were a no-show. A good rain on September 1st and a couple of following showers mid-month have produced a flush of leaves and galls locally, though. Asphondylia pila galls are abundant, while A. silicula, A. clavata and A. fabalis (all leaf galls) are fairly common as well.
Ron Russo's updated guide is now available, and it adds one further creosote bush Asphondylia gall, an apical, scimitar-shaped gall provisionally labeled Asphondylia sp. and named "scimitar-leaf-gall midge". The description: "This midge induces flat-sided, sword-shaped, striated, monothalamous bud galls on creosote bush. These galls are green when fresh but turn brown with age. The laterally-flattened sides are furrowed with shallow ridges. The apex of the gall is usually obtuse, and the whole gall is arched. These distinctive galls are almost all on terminal buds and stand out from normal leaves. Adults have not been reared for identification to species level. Their behavior is likely similar to that of other Asphondylia adults."
Gall season seems to be later this year compared to last. I've been spot-checking the creosote bushes near the house over the summer, but am only now starting to find new galls.
Over time, I hope the project will accumulate observations of all the known species of Asphondylia that induce galls on the creosote bush, and perhaps find new ones. Secondly I hope to learn how to correctly ID these galls (I have a history).
Many people know of and use Ronald Russo's field guide to California galls, but unfortunately it is out of print. It has great photos of fourteen known species, plus that of an unnamed species of Contarinia that also induces galls on creosote bushes (that species can't be added to the project for obvious reasons.)
The Gagné and Waring article mentioned in the project description has some drawings of the galls, and brief descriptions of each. If you want to take a deep dive into adaptive radiation in the Asphondylia auripila group, here you go.
The stem galls are relatively large and easy to find. I'm still having an issue separating A. foliosa and A. resinosa though. Some galls are quite large (to 6 mm) and leafy, though the leaves are essentially glued to each other with resin. A. resinosa is quite small (3 mm according to Russo).
Leaf galls are more difficult. They are smaller, harder to photograph, and some are hard to separate. A. clavata and A. pila are nearly identical, the latter being characterised by hair present on the gall. Some galls have just a bit of fuzz. Still A. pila? (A. pila is a name change from A. pilosa in Russo and in the Gagné and Waring article.)
There are also some unknowns that to my eyes don't fit any description but are certainly galls. Here's one, and here's another.
In time and with added observations maybe some of those problems will be resolved.
